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How to extend a pulse width without clock!
- 09-03-2003

Re: How to extend a pulse width without clock!
delay.. but you might find another signal which you can use as a clock A0
if you have a micro.. or ALE.. WR.. RD something like that.. failing that..
an RC off chip :-)
Simon


Re: How to extend a pulse width without clock!

uups, bad luck - not recommended but if you have enough free pins and logic
you and if the timing is not critical it is possible to make free running
oscillator without external RC components, just connect uneven count of
inverters in ring (ie 3 inverters) as this is astable it will oscillate
with pretty high frequency, this could be divided down, but from about
40MHz down to 100ms its pretty long counter ... and this approuch
really isnt 'recommended'
as other options build simple RC on IO cells and use that signal
antti

Re: How to extend a pulse width without clock!

I have delayed strobe signals several hundred nS with an external series
resistor, and used the input capacitance of the chip as the C of the RC
network. For mS, you will need an external capacitor, of course. if you
want the delay to be asymmetric (like a one-shot), you might need to
put a diode in parallel with the R. You feed the signal out one pin,
through a series R, to a pin loaded with a cap to ground, and then take
the signal in from that pin. This may cause multiple pulses with a
delay this long, however. So, you might end up using a 74HC4538
or similar one shot, or a 74HC14 Schmitt trigger to prevent the
pulses as the output of the RC crosses the threshold.
Jon
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